The invention is based on a method described in U.S. Pat. No. 7,703,192 and the stator or rotor produced by this method which published application is hereby incorporated by reference. It provides that a distributed wave winding is assembled from two separately interlaced wire groups of preferably rectangular winding wires, in which each group is created by winding on a striplike flat former, by the intersection of the wires in the head portion regions, and by ensuing flat pressing. The two winding halves pressed flat separately in one ply at the end lie in a defined plane each in the stator or rotor slots, without being intertwined/interlaced with one another. The respective winding wires, associated in pairs and located in the same slots, of the two strands are joined only by soldering on one end. Although a double or two-ply layer formed of both winding halves located one above the other supposed to have the thickness of twice the wire thickness, at certain points three wires intersect at such close spacing that a certain lack of uniformity in thickness occurs, and this deficiency increases when there are a plurality of layers.
Distributed wave windings in which all the winding wires are interlaced with one another to form one coherent strand are described in U.S. Pat. Nos. 6,750,581 B2, 6,759,779 B2, 6,826,823 B2 and 6,862,797 B2. No production method is disclosed, but if, as is normally desired, the prefabricated wave winding shall extend multiple times about the circumference of a stator or rotor and thus form a plurality of layers, in those areas where the transition from one layer to the next takes place, an irregularity must be incorporated into the strand of interlaced wires, making production by machine more difficult.
From European Patent Disclosure EP 1 469 579 A1, it is furthermore known to produce a distributed wave winding for a stator or rotor by winding all the winding wires that form a two-ply layer parallel to one another onto a former of hexagonal cross section in a single winding operation, the former having two parallel side faces, which are provided with transverse slots and are joined on both long edges by gable-shaped end faces. The winding operation thus proceeds helically along the former, but the inclination is limited to the unslotted, gable-shaped end faces, while the winding wires in the slots of the parallel side faces extend without a slope, transversely to the longitudinal center axis of the former. Each time the parallel winding wires are wound about the former, some of the wires are placed in slots located diametrically opposite other slots that have been occupied earlier during the same winding operation. Once a certain number of windings has been reached, the multi-part former is reduced in its cross section and pulled out of the coil that has been formed. After that, the coil of hexagonal cross section is pressed flat in two plies, and the straight wire segments created on both side faces of the former are pressed against one another.
In this last-described winding method, the wires are placed continuously, with a constant inclination, onto the gable-shaped end faces of the former. Because of the residual intrinsic elasticity, however, they do not rest flat there, nor are they pressed from outside against these faces, and they are not retained in slots. The bending of the wires about the edges that define the gable-shaped end faces, in conjunction with the bending for attaining the axial inclination of the wire windings, causes torsion of the rectangular wires throughout the area of the head portion, which proves harmful in the phase between when the coil is removed from the former and the flat pressing is done. Normally, in this known winding method, the outer side face of a wire, resting on a side face of the former, should also be located on the outside over the entire length of a head portion. However, both the torsional stress in the wire and the bending edges extending obliquely to its longitudinal edges cause twisting about the longitudinal axis of the wire and bends, so that upon the flat pressing, the wire portions located one above the other or intersecting one another are in part pressed with their side edges instead of with the side faces, against one another, and the parallel course of the wires in the head portion region is not assured, either.